Re: [PATCH v2] KVM: x86: Make register state after reset conform to specification

[Gleb Natapov <gleb@redhat.com>]

On Mon, Dec 03, 2012 at 02:46:55PM +0100, Julian Stecklina wrote:
> Floating point initialization is moved to kvm_arch_vcpu_init. Added general purpose
Actually Intel SDM Table 9-1 footnote 5 says: "The state of the x87 FPU and MMX
registers is not changed by the execution of an INIT.". So lets drop
this part of the patch for now since vcpu_reset() does not distinguish between reset
and INIT currently.

> register clearing to the same function. SVM code now properly initializes
> EDX.
> 
> Signed-off-by: Julian Stecklina <jsteckli@os.inf.tu-dresden.de>
> ---
>  arch/x86/kvm/cpuid.c |  1 +
>  arch/x86/kvm/svm.c   |  7 +++++--
>  arch/x86/kvm/vmx.c   |  7 +------
>  arch/x86/kvm/x86.c   | 12 +++++++++++-
>  4 files changed, 18 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 0595f13..aa468c2 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -659,6 +659,7 @@ void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
>  	} else
>  		*eax = *ebx = *ecx = *edx = 0;
>  }
> +EXPORT_SYMBOL_GPL(kvm_cpuid);
>  
>  void kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
>  {
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index baead95..642213a 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -20,6 +20,7 @@
>  #include "mmu.h"
>  #include "kvm_cache_regs.h"
>  #include "x86.h"
> +#include "cpuid.h"
>  
>  #include <linux/module.h>
>  #include <linux/mod_devicetable.h>
> @@ -1190,6 +1191,7 @@ static void init_vmcb(struct vcpu_svm *svm)
>  static int svm_vcpu_reset(struct kvm_vcpu *vcpu)
>  {
>  	struct vcpu_svm *svm = to_svm(vcpu);
> +	u32 dummy, eax;
>  
>  	init_vmcb(svm);
>  
> @@ -1198,8 +1200,9 @@ static int svm_vcpu_reset(struct kvm_vcpu *vcpu)
>  		svm->vmcb->save.cs.base = svm->vcpu.arch.sipi_vector << 12;
>  		svm->vmcb->save.cs.selector = svm->vcpu.arch.sipi_vector << 8;
>  	}
> -	vcpu->arch.regs_avail = ~0;
> -	vcpu->arch.regs_dirty = ~0;
> +
> +	kvm_cpuid(vcpu, &eax, &dummy, &dummy, &dummy);
You are passing uninitialized eax here. It is used by kvm_cpuid().
Should set it to 1.

> +	kvm_register_write(vcpu, VCPU_REGS_RDX, eax);
>  
>  	return 0;
>  }
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index ff66a3b..363fb03 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -3942,7 +3942,7 @@ static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
>  	u64 msr;
>  	int ret;
>  
> -	vcpu->arch.regs_avail = ~((1 << VCPU_REGS_RIP) | (1 << VCPU_REGS_RSP));
> +	vcpu->arch.regs_avail = ~(1 << VCPU_REGS_RIP);
VCPU_REGS_RIP is part of registers array too, why not dropping the line?

>  
>  	vmx->rmode.vm86_active = 0;
>  
> @@ -3955,10 +3955,6 @@ static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
>  		msr |= MSR_IA32_APICBASE_BSP;
>  	kvm_set_apic_base(&vmx->vcpu, msr);
>  
> -	ret = fx_init(&vmx->vcpu);
> -	if (ret != 0)
> -		goto out;
> -
>  	vmx_segment_cache_clear(vmx);
>  
>  	seg_setup(VCPU_SREG_CS);
> @@ -3999,7 +3995,6 @@ static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
>  		kvm_rip_write(vcpu, 0xfff0);
>  	else
>  		kvm_rip_write(vcpu, 0);
> -	kvm_register_write(vcpu, VCPU_REGS_RSP, 0);
>  
>  	vmcs_writel(GUEST_DR7, 0x400);
>  
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 2966c84..9640ea5 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6045,6 +6045,8 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
>  
>  int kvm_arch_vcpu_reset(struct kvm_vcpu *vcpu)
>  {
> +	int ret;
> +
>  	atomic_set(&vcpu->arch.nmi_queued, 0);
>  	vcpu->arch.nmi_pending = 0;
>  	vcpu->arch.nmi_injected = false;
> @@ -6066,7 +6068,15 @@ int kvm_arch_vcpu_reset(struct kvm_vcpu *vcpu)
>  
>  	kvm_pmu_reset(vcpu);
>  
> -	return kvm_x86_ops->vcpu_reset(vcpu);
> +	memset(vcpu->arch.regs, 0, sizeof(vcpu->arch.regs));
> +	vcpu->arch.regs_avail = ~0;
> +	vcpu->arch.regs_dirty = ~0;
> +
> +	if ((ret = fx_init(vcpu)) != 0) goto out;
> +
> +	ret = kvm_x86_ops->vcpu_reset(vcpu);
> +out:
> +	return ret;
>  }
>  
>  int kvm_arch_hardware_enable(void *garbage)
> -- 
> 1.7.11.7

--
			Gleb.